The present subject matter generally concerns improved termination features for multilayer electronic components, and more particularly relates to plated terminations for multilayer electronic components, such as capacitors, resistors, etc. or for integrated passive components. The subject termination design utilizes selective arrangements of internal and/or external electrode tabs to facilitate the formation of plated electrical connections. The external connections are preferably made whereby the provision of typical thick film termination stripes is eliminated or greatly simplified.
Many modern electronic components are packaged as monolithic devices, and may comprise a single component or multiple components within a single chip package. One specific example of such a monolithic device is a multilayer capacitor or capacitor array, and of particular interest with respect to the disclosed technology are multilayer capacitors with interdigitated internal electrode layers and corresponding electrode tabs. Examples of multilayer capacitors that include features of interdigitated capacitor (IDC) technology can be found in U.S. Pat. No. 5,880,925 (DuPré et al.) and U.S. Pat. No. 6,243,253 B1 (DuPré et al.). Other monolithic electronic components correspond to devices that integrate multiple passive components into a single chip structure. Such an integrated passive component may provide a selected combination of resistors, capacitors, inductors and/or other passive components that are formed in a multilayered configuration and packaged as a monolithic electronic device.
Selective terminations are often required to form electrical connections for various monolithic electronic components. Multiple terminations are needed to provide electrical connections to the different electronic components of an integrated monolithic device. Multiple terminations are also often used in conjunction with IDC's and other multilayer arrays in order to reduce undesirable inductance levels. One exemplary way that multiple terminations have been formed in multilayer components is by drilling vias through selected areas of a chip structure and filling the vias with conductive material such that an electrical connection is formed among selected electrode portions of the device.
Another way of forming external terminations for the subject devices is to apply a thick film stripe of silver or copper in a glass matrix to exposed portions of internal electrode layers, and subsequently plating additional layers of metal over the termination stripes such that a part is solderable to a substrate. An example of an electronic component with external electrodes formed by baked terminations and metal films plated thereon is disclosed in U.S. Pat. No. 5,021,921 (Sano et al.). The application of terminations is often hard to control and can become problematic with reduction in chip sizes. U.S. Pat. No. 6,232,144 B1 (McLoughlin) and U.S. Pat. No. 6,214,685 B1 (Clinton et al.) concern methods for forming terminations on selected regions of an electronic device.
The ever-shrinking size of electronic components makes it quite difficult to print termination stripes in a predetermined area with required precision. Thick film termination stripes are typically applied with a machine that grabs a chip and applies selective terminations with specially designed wheels. U.S. Pat. No. 5,944,897 (Braden), U.S. Pat. No. 5,863,331 (Braden et al.), U.S. Pat. No. 5,753,299 (Garcia et al.), and U.S. Pat. No. 5,226,382 (Braden) disclose mechanical features and steps related to the application of termination stripes to a chip structure. Reduced component size or an increased number of termination contacts for an electronic chip device may cause the resolution limits of typical termination machines to become maxed out.
Other problems that can arise when trying to apply selective terminations include shifting of the termination lands, mispositioning of terminations such that internal electrode tabs are exposed or missed entirely, and missing wrap-around termination portions. Yet further problems may be caused when too thin a coating of the paint-like termination material is applied or when one portion of termination coating smears into another causing shorted termination lands. These and other concerns surrounding the provision of electrical termination for monolithic devices create a need to provide cheap and effective termination features for electronic chip components.
In light of component miniaturization and concerns with providing terminations that do not short together, especially when positioning multiple components in proximity on a circuit board, U.S. Pat. No. 6,380,619 (Ahiko et al.) provides a chip type electronic component having external electrodes that are spaced at predetermined distances from side surfaces of a ceramic substrate. More particularly, electronic components having three-sided terminations as opposed to more conventional five-sided terminations are disclosed. Such components with three-sided terminations are more easily provided in an adjacent relationship with one another without shorting together distinct component terminations. Some embodiments disclosed in Ahiko et al. include electroplated films applied to the exposed portions of individual electrodes.
Yet another known option related to termination application involves aligning a plurality of individual substrate components to a shadow mask. Parts can be loaded into a particularly designed fixture, such as that disclosed in U.S. Pat. No. 4,919,076 (Lutz et al.), and then sputtered through a mask element. This is typically a very expensive manufacturing process, and thus other effective yet more cost efficient termination provisions may be desirable.
U.S. Pat. No. 5,880,011 (Zablotny et al.), U.S. Pat. No. 5,770,476 (Stone), U.S. Pat. No. 6,141,846 (Miki), and U.S. Pat. No. 3,258,898 (Garibotti), respectively deal with aspects of the formation of terminations for various electronic components.
Additional background references that address methodology for forming multilayer ceramic devices include U.S. Pat. No. 4,811,164 (Ling et al.), U.S. Pat. No. 4,266,265 (Maher), U.S. Pat. No. 4,241,378 (Dorrian), and U.S. Pat. No. 3,988,498 (Maher).
While various aspects and alternative features are known in the field of electronic components and terminations therefor, no one design has emerged that generally addresses all of the issues as discussed herein. The disclosures of all the foregoing United States patents are hereby fully incorporated into this application by reference thereto.